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Jan 26, 2007 12:31 am US/Mountain
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Colder Weather Needed To Kill Beetle Infestation
Good Question: Could This Winter End The Bark Beetle Infestation?
by Alan Gionet
DENVER (CBS4) ―
The area of Colorado's forests now infested with bark beetles has reached over one million acres. That's more than four times the size of Rocky Mountain National Park. Mountain pine beetles and spruce beetles started their most recent spread at the end of the 1990s. Each year, beetles hatch and spread to new trees, creating new infestations. They bring a deadly fungus with them that cuts off the tree's ability to transport water and nutrients.
Scientists heave been working on a solution, but so far there is only one sure way to kill the beetles and stop the spread. Cold. Deep cold.
"We can hope for that. It's a very uncommon occurrence," says the U.S. Forest Service's Andy Cadenhead. "If they were to freeze, which can happen if it gets really cold, then ice crystals will form and when ice expands when it forms then it can break the cells and that would kill the beetle."
Cadenhead notes that below zero cold helped turn the tide against a beetle infestation in Summit and Eagle Counties in the mid-80s.But how cold? Temperatures in Fraser bottomed out at 31 below in Fraser just recently. In Kremmling, 32 below. But even cold like that is not enough.
Most of those official temperature measurements come in the towns, which are located in high mountain valleys. Cold air sinks and the temperatures on the mountainsides where the trees are being hit are a little warmer. Most of the beetles remain low on the trunks of the trees, where the snow is an insulator.
Spruce beetles move down in the trees in the winter. And come the colder months the beetles have a remarkable self-protection mechanism. The beetles go into a semi-hibernation called, diapause.
"Their system has shut down," says Cadenhead. "Some of the water's been expelled from their body. And they're just getting through this."
While the water is expelled, they produce a substance very similar to the ethylene glycol that is a common ingredient in anti-freeze.
"Their body temperature needs to get down to 29 degrees blow zero," says Kim Vogel of the Forest Service.
The ambient air temperature needs to be below that. So getting cold enough, is rare.
"As as the beetles themselves get colder than about minus 20 degrees Fahrenheit there's some mortality," says Cadenhead. "And right about minus 30 degrees under the bark, approximately half the larvae will be killed. Once it gets to approaching 40 or 50 below, under the bark, it's near total mortality."
The experts say some have probably died this winter, but it would have to be at least minus 40 overnight to stop the beetles. It's been cold. But it hasn't been that cold. The infestation marches on.
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